Bacterial engineering attempts to harness the internal machinery of bacteria to generate desired chemicals or to break down unwanted environmental contaminants. One method for controlling the output of bacteria is directed evolution where the production or destruction of the target chemical becomes critical for cell survival. Directed cell evolution is enhanced by the ability to rapidly separate cells based on their expressed behavior. Devices that can enable this rapid cell sorting are needed. The methods, devices, and systems discussed herein addresses these and other needs.